#define  _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int frog(int n)
{
    if (n == 1)
    {
        return 1;
    }
    if (n == 2)
    {
        return 2;
    }
    return frog(n - 1) + frog(n - 2);
}
int main()
{
    int n;
    scanf("%d", &n);
    int ways = frog(n);
    printf("%d\n", ways);
    return 0;
}
